Crop Development--Precautions  06/06/18 11:47:45 AM

2018 Summer Field Tour Details
The 2018 plot tours will continue on Tuesday June 12th  at our plot on the West side of Mynard Nebraska—1 mile South of our plant—1/4 west on Mynard Road OR 1-1/4 mile West of HWY 75 on Mynard Road—South Side of the Road.   The tours would last no longer than 1.5 hours and address any current agronomic issues as well as allow the attendees to monitor developmental progress of Asgrow and Dekalb genetics throughout the growing season.  We conduct these tours RAIN OR SHINE—If it is raining or has significantly rained we hold the discussion in our seed building. 
Our Tentative Summer Tour Schedule
Date                                        Time                            Location
Tuesday June 12th                9:00 a.m.                     Mynard
This tour includes a discussions (1) In-season crop fertility—the value of sampling soil and tissue in June (2) The impact of hail--simulation on corn and soybeans  (3) Post-Emergence Soybean Herbicide Applications  (4) and as always Developmental looks and the new genetic lineup for 2019
Bring a Friend and we will see next Tuesday June 12th at 9:00 a.m. 
Tuesday June 12th                   9:00 a.m.                     Mynard
Tuesday June 26th                   9:00 a.m.                     Mynard
Tuesday July 10th                    9:00 a.m.                     Mynard
Tuesday July 24th                    9:00 a.m.                     Mynard
Tuesday August 7th                 9:00 a.m.                     Mynard
Tuesday August 21th               9:00 a.m.                     Mynard
Wednesday August 29th ,WBI  Fall Mtg.  –Stay tuned for details
Most of the corn is between the 7-8 leaf stage of development.   Early Corn Planted on April 20th  has now accumulated approximately 850 (GDD).  Ear shoots have been initiated and the tassel can be seen in the developing whorl of the corn plant. The seminal and nodal roots are fully developed and the nodal roots will continue to further develop with every additional node of plant (on average 7-10 nodes total). 
Growing Degree Days for Corn Growth Stages for a 108 day Hybrid
Stage                                       GDD (Growing Degree Days--base 50)        
Emergence                                                      120
2 leaf-V2                                                         200
V6—tassel initiation                                       475
V10                                                                 740
V14                                                                 1000
VT (tassel emergence)                                    1150
Silking                                                             1400
R4 (Kernel dough stage)                                 1925
R5 (Kernel dent stage)                                    2450
R6 (physiological maturity—black layer)      2700
*courtesy of Hollinger (University of Nebraska)
When corn grows quickly water and nutrients are consumed at an amazing rate.  Water use in corn in Eastern Nebraska on average transpires between 25-28” of water through the plants during the growing season.  The corn plant is trying to use between 0.10” and 0.15” of moisture transpired through the plant each day. The plant roots are in the top 6-8” of the soil profile and a typical corn plant can root up to 4 feet deep. Forty percent of water and fertility absorption occurs within the top 12”, 30% in the second foot, 20% in the third foot, and 10% in the fourth foot of the soil profile.
The following table demonstrates the amount of soil water a corn plant can typically use per day.
Growth Stage                          Inches Water Use/Day
1-4 leaf                                                            .02 - .05
5-8 leaf                                                            .05 - .10
8-10 leaf                                                          .10 - .15
11-14 leaf                                                        .15 - .20
14-18 leaf                                                        .20 - .25
19 leaf - blister                                                .25 - .30
Milk - soft dough                                            .20 - .25
Hard dough - early dent                                  .15 - .20
Mid - full dent                                                .10 - .15
Soybeans on average transpire between 22-25” inches of water through the plants each year. They use 65% of total water use during the reproductive stage (flowering/podding) of development.  Many soybean fields are approaching the 3 and 4th trifoliate stage of growth.  Nitrogen-fixation (nodulation) has begun with lateral root development occurring in the top 6 inches of the soil profile.  Soybean root development can reach 5 and 6 foot depths, but like corn, the largest concentration of root development and water uptake occurs within the top 2 feet of the soil profile. The following table demonstrates the amount of water used be a typical soybean plant per day.
Growth Stage                          Inches Water Use/Day
Germination/Emergence                     .1 - .15
Vegetative Growth                             .15 - .20
Flowering                                            .25 - .30
Pod Development                               .20 - .25
Seed Fill                                              .15 - .20
Maturation                                          .05 - .10
How is your stand?  This is always a topic in June which we encourage.  Overall stand establishment appears to be fairly good.  Yes, there are examples of where excessive residue from last year’s crop has slowed emergence and initial growth and the crop is uneven—especially in soybeans.  That, combined with other factors from last year and this year, always will play a role.  Genetic selection and impact always in question, especially when Side by Side comparisons exist in the same field.  Maybe equipment issues had a good/bad result in your stand establishment.  Lingering herbicide residue from last year’s crops also have popped up in conversation and how it did/could affect stands. 
Whether you have done this via the windshield or during post-emergence herbicide applications, many of you have scouted your fields and determined what has worked and what needs work.  Remember that October is along ways away from a crop development standpoint and many things that appear questionable today can have little to no affect on yield at harvest.  Stand establishment is vital in achieving a good yielding crop.  If you are unsatisfied with your stand, consider all of these fore-mentioned topics when thinking about changes for the next season.    
Yellow, streaked corn is an issue in some areas.   A very quick growth spurt can temporarily cause yellow streaks between the veins of the leaves and/or yellow the whorl.  Under quick growth conditions, the plant cannot keep up with the chlorophyll production demand of the plant causing the yellowing to occur even though sufficient fertility may exist.   Likely this is due to under-developed root systems in these situations. 
What becomes of the nitrate in these situations? Nitrate, which is the plant available form of nitrogen, and also water soluble, is subject to leaching, or can denitrify if saturated soil conditions exist. How far nitrate can leach is dependent largely by how far down the water moves. One inch of rain on a dry silt loam soil will penetrate about 4-6”. Additional water can move nitrate down further and out of the root zone of small corn plants. However, in heavier soils, especially with high clay content in the subsoil, leaching is reduced due to smaller pore spaces, and less mass flow through the profile. As roots grow down, they can get to the nitrate, providing it doesn’t leach below about 4’. Remember too, that as water evaporates from the soil, water moves upward and can take nitrate with it, bringing some back to upper levels of the soil profile.
Denitrification occurs when anaerobic (require little or no oxygen) bacteria increase in activity and break down the nitrate molecule to gaseous forms of nitrogen, which in turn is lost to the atmosphere. This can occur if soils are saturated for at least two days, at temperatures above 60 degrees. Losses can be 2 lbs./acre/day or more as reported by the University of Nebraska. Another corn belt study cites losses of 4-5% per day of saturation. In this same study, saturated soils for 5-6 days cost about 10-20 bu/acre in lost corn yield. Again, as the water drains and the soil returns to field capacity (which is defined as the amount of water in the soil remaining after having been saturated, and after free drainage has stopped), the activity of the anaerobic bacteria will decline and denitrification will cease. So, unless water has “ponded” for an extended period of time, denitrification should be short lived.
Should more nitrogen be applied? Assuming that adequate rates of nitrogen fertilizer was applied to begin with, the answer in most cases will be “no”. If an area is slow to return to normal color, and the area is large enough to make side-dressing feasible, then applying an additional 40 lbs could be justified.
Soybean development  Much of the soybean acres are between the V2 and the V3 stage (plants 4-6 inches tall) with 3-th trifoliates completely unfolded—each “V” stage indicates the number of trifoliates present on the plant. At the V2-V3 stage of development, given normal weather patterns, the plant normally develops a new trifoliate every 5-7 days and when it reaches the V6 stage can develop a new V stage every 3 days.     Vegetative growth from emergence to the appearance of the first flower is normally 6-8 weeks.  The soybean plant is light (photoperiod) sensitive meaning it makes the transition from vegetative growth to reproductive (flowering) growth based upon the number of dark hours within a 24-hour period.    Active flowering of indeterminate varieties usually occurs 20 days after the first day of summer (June 21st) meaning it should start about July 11th.    Plant growth of indeterminate varieties continues after flower development and can double or triple in height after flowering begins if the right weather and fertility conditions are present.  How big will the plant be 20 days from now plays a sizable role to maintain a reasonable yield goal.  Flowering on average begins when the plant is 18 to 24 inches tall and in the V7 to V10 stage. 
Soybeans after June 10th--Corn and soybeans are unlike in what promotes them into their respective reproductive phases of development.  Corn does it through the accumulation of heat units (GDU’s).  Soybeans do it through day length or the amount of sunlight the plant is exposed too.   So, we are past the optimal time for planting corn in order to maximize yield potential.  With soybeans it is common knowledge that they should be in the ground at least in mid-May and prior to Memorial Day in order to achieve the greatest yield potential—
Hail has thinned my stand!!.  Some early planting soybean fields are experiencing some stand establishment reductions due to recent storms and/or insects, etc..  Should you replant them?  Should you use the same maturity on the second planting?  Replant soybeans only if you have a stand loss of greater than 40% of your original seeding rate.  Use the same maturity of soybean that you initially planted.  A week from now, replant soybeans only if you have a stand loss of greater then 50% of your original seeding and still use the same maturity of soybean that you initially planted.  Once the calendar gets into the 20’s of June is the only time we would decrease the maturity of the soybean being used by ½ of a maturity point (From a Group 3 to a Group 2.5).  Yield potential in soybeans is always greater with the maturity adapted for your geography.  As we get further past June 10th, you are taking a yield potential reduction no matter how you look at it.  Still, you have the greatest potential with genetics developed for your growing region until the calendar reaches the 20’s of June.
Soybean Post-Emergence Precautions-If you have experienced soybean injury due to storm damage, we would suggest you wait at least a week after the storm before any post-emergence herbicide application occurs.  Once new growth occurs (visible healthy leaves and tissue) then it is certainly time to spray.   
Weeds are growing fast--Below is an example of the value of a Soybean Pre-emergence treatment.  This was taken yesterday (June 5th) at our demonstration plot at Mynard.  On the left is the un-treated check and on the right is the pre-emergence application of 5 oz/acre of Sencor + 6 oz/acre of Zidua Pro + 48 ox of Tomahwk 5 as a burndown/Pre-emergent treatment at planting. 

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